If the 'wrong' cap isn't causing a problem because it's value is too low, why replace it with another cap that's the wrong value? Wait until you order parts and order the correct part. Then replace the 0.1uf.

It is not about what correct parts fits that, I already know. But I want to learn about what does that capacitor do? Why is the value so high on that capacitor and why is the value lower on the same capacitor in different amps? Why not use another version of capacitor not mylar?

As I mentioned before, the capacitors shunt (bypass) high frequency noise to ground.

The capacitor is placed at the terminals so that's it's most effective at shunting the noise and prevents it from getting into/out of the amp.

Aluminum electrolytics are not as good as ceramic or film capacitors because they have relatively high ESL (Equivalent Series Inductance) and the loss (inability to pass efficiently pass current) at higher frequencies is greater.

When low impedance at high frequencies is needed and the total capacitance needed is not significant, ceramic, film or tantalum capacitors are used.

The value used is up the the designer, in most cases. You can vary the capacitance significantly and make no audible difference. If the amp must pass certain tests for noise (on the power supply lines), the designer may have to increase the capacitance to meet spec. 0.1uf is a good starting point. If the amp is generating too much high frequency noise on the supply lines (across B+ and ground), the designer may increase the value.